Method and apparatus for improving power amplifier efficiency in wireless communication systems having high peak to average power ratios

ABSTRACT

A power management system and method for a wireless communication device generates an average desired transmit power signal based on at least one of a received signal strength indicator signal and a power control instruction signal from a base station. A power supply level adjustment signal is generated based on the data parameters of an outgoing data stream and at least one environmental information signal. A combination of the power supply level adjustment signal and the average desired transmit power or a gain control signal and an altered version of the power supply level adjustment signal is used to generate a variable power supply signal that is provided to an output amplifier block for sufficiently generating outgoing wireless device radio signals while reducing power loss in the output amplifier block.

FIELD OF THE INVENTION

This invention relates to wireless communication devices. Moreparticularly, it relates to a method and apparatus for improving poweramplifier efficiency in wireless communication systems having variabletransmit power in a large range and/or high peak to average powerratios.

BACKGROUND OF THE INVENTION

Handheld wireless communication devices and other types of wirelesstransmitters are typically powered by one or more internal batteries. Amajor performance criterion for such devices is their battery life,which is typically defined as the time period for which the battery willpower the device on a single charge. A large portion of battery power isconsumed in a power amplifier section of the wireless device'stransmitter. The power amplifier section amplifies the power of a signalto be transmitted from a comparatively low internal power level to asubstantially higher power level required for wireless communicationwith remote base stations and other devices. Improving the poweramplifier efficiency, or more generally the transmitter efficiency,would reduce power consumption and increase battery life.

Accordingly, there is a need for a system that provides improved poweramplifier efficiency, or more generally, improved transmitterefficiency.

SUMMARY OF THE INVENTION

The invention provides a power management system that supplies avariable power supply signal to a power amplification stage of an outputpower amplification block of a wireless communications device. Thedesired power of an amplified transmission signal, that is produced bythe power amplification stage, is estimated and used to vary the powersupply voltage that is provided to the output power amplifier, to reducepower loss in the power amplification stage. Advantageously, theestimated desired power is adjusted according to at least oneenvironmental information signal. For instance, at least one of atemperature information signal, a battery condition signal and theoperating frequency of the wireless communications device can be used toaugment the estimated desired power level to provide more accuratecontrol of the power supply signal.

In a first aspect, the invention provides a power management system forproviding a variable power supply signal to an output power amplifierblock in a wireless communication device. The power management systemcomprises an average power and gain control block for providing a gaincontrol signal and an average desired transmit power signal, the averagedesired transmit power signal being generated in response to at leastone of a power control instruction signal and a received signal strengthindicator signal; an environmental sensor unit for providing at leastone environmental information signal; a power supply level adjustmentgenerator connected to the environmental sensor unit for providing apower supply level adjustment signal in response to a data parameterindication of a baseband outgoing data stream to be transmitted by thewireless communication device and the at least one environmentalinformation signal; and, a power supply means connected to the averagepower and gain control block for providing the variable power supplysignal to the output power amplifier block in response to a combinationof the average desired transmit power signal and the power supply leveladjustment signal or a combination of the gain control signal and analtered version of the power supply level adjustment signal.

The environmental sensor unit comprises at least one of a temperaturesensor for providing a temperature information signal as part of the atleast one environmental information signal, the temperature informationsignal being related to the temperature of the hardware of the wirelesscommunications device; and, a battery condition sensor for providing abattery condition information signal as part of the at least oneenvironmental information signal, the battery condition informationsignal being related to a battery used to power the wirelesscommunication device. A frequency information signal related to thefrequency at which the baseband outgoing data stream will be transmittedmay also be included as part of the environmental information signal.

The average power and gain control block may comprise an average powerlevel block for generating the average desired transmit power signal,and a gain control block connected to the average power level block forgenerating the gain control signal. Further, the power supply meansincludes a power supply control block for providing a power controlsignal and a switch converter connected to the power supply controlblock for providing the variable power supply signal in response to thepower control signal, and wherein the power supply means is connected tothe power supply level adjustment generator for providing the variablepower supply signal to the output power amplifier block in response to acombination of the average desired transmit power signal and the powersupply level adjustment signal.

Alternatively, the power supply level adjustment generator can producean altered version of the power supply level adjustment signal accordingto the gain control signal provided by the average power and gaincontrol block, and the power supply means comprises: a summer connectedto the average power and gain control block and the power supply leveladjustment generator for summing the gain control signal and the alteredversion of the power supply level adjustment signal to generate a firstpower control signal; a clipper connected to the summer for receivingthe first power control signal and generating a second power controlsignal; a switch converter connected to the clipper for receiving thepower control signal and generating the variable power supply signal;and, a reverse mapper connected to the power supply level adjustmentgenerator and the average power and gain control block for receiving anenvironmental signal and an altered version of the gain control signalrespectively and generating a clipper adjustment signal, the reversemapper also being connected to the clipper for providing the clipperadjustment signal to the clipper for adjusting the performance of theclipper.

Preferably, the power supply means is configured to maintain thevariable power supply signal above a minimum voltage level. Further, thepower supply level adjustment generator may be implemented by aplurality of look-up tables, wherein one look-up table is provided foreach environmental information signal and the data parameter indication,and the outputs of each look-up table are combined to generate the powersupply level adjustment signal. Alternatively, at least one of thelook-up tables may be implemented by a corresponding formula.

Further, the power supply block is calibrated by:

-   (i) transmitting the wireless device radio signals at a constant    power level from the wireless communication device while monitoring    an Adjacent Channel Power Ratio (ACPR);-   (ii) reducing the magnitude of the variable power supply signal    while maintaining constant output power in the wireless device radio    signals;-   (iii) recording the magnitude of the variable power supply signal    when the ACPR has increased to a pre-specified design target;-   (iv) increasing the output power of the wireless device radio    signals and repeating steps (i) to (iii) for several output power    levels; and,-   (v) computing an ideal transfer function for deriving the power    control signal for controlling the switch converter.

The power supply block may further be calibrated by:

-   (vi) repeating steps (i) to (v) for several different wireless    communication devices to obtain an average transfer function; and,-   (vii) performing curve fitting on the average transfer function.

Further, the power supply level adjustment generator is calibrated by:

-   (viii) loading the power supply level adjustment generator with a    value which causes the output power amplifier block to operate at a    lowest transmission power point;-   (ix) calibrating the transmission power until the output power of    the output power amplifier block slightly exceeds a target power    determined for a power supply voltage level;-   (x) interpolating the output value of the average power level block    and loading this interpolated output value, after adjustment by a    reverse mapper, into the power supply level adjustment generator;-   (xi) adjusting the transmission power level to a value slightly    below the target power; and,-   (xii) increasing the value of the transmission power level and    repeating steps (viii) to (xi) until a maximum specified    transmission power point is reached.

In another aspect, the invention provides a method of supplying avariable power supply signal to an output power amplifier block in awireless communications device that receives an incoming data streamfrom a base station radio signal and transmits an outgoing data streamin a wireless device radio signal, the method comprising:

-   (a) detecting at least one of a signal strength of the base station    radio signal to produce a received signal strength indicator signal,    and a power control instruction signal in the base station radio    signal;-   (b) generating an average desired transmit power signal in response    to at least one of the received signal strength indicator signal and    the power control instruction signal;-   (c) generating at least one environmental information signal for    obtaining information about the environment of the wireless    communications device;-   (d) generating a power supply level adjustment signal based on a    data parameter indication of a baseband outgoing data stream and the    at least one environmental information signal; and,-   (e) combining one of the average desired transmit power signal and    the power supply level adjustment signal or a gain control signal    and an altered version of the power supply level adjustment signal    to generate the variable power supply signal, the gain control    signal being derived based on at least one of the received signal    strength indicator signal and the power control instruction signal,    and providing the variable power supply signal to the output power    amplifier block.

Step (c) of the method preferably includes at least one of:

-   (i) generating a temperature information signal related to the    temperature of the hardware of the wireless communications device    and providing the temperature information signal as part of the at    least one environmental information signal;-   (ii) generating a battery condition information signal related to a    battery used to power the wireless communications device and    providing the battery condition information signal as part of the at    least one environmental information signal; and,-   (iii) generating a frequency information signal related to the    frequency at which the outgoing data stream is transmitted and    providing the frequency information signal as part of the at least    one environmental information signal.

Step (e) of the method may include:

-   (iv) combining the average desired transmit power signal and the    power supply level adjustment signal to generate a power control    signal; and,-   (v) converting the power control signal into the variable power    supply signal.

Alternatively, step (e) of the method may include:

-   (iv) adding an altered version of the power supply level adjustment    signal and the gain control signal to provide a first power control    signal, the altered version of the power supply level adjustment    signal being generated based on the derivation of the gain control    signal;-   (v) clipping the first power control signal to provide a second    power control signal; and,-   (vi) converting the second power control signal into the variable    power supply signal.

Step (v) includes providing a clipper adjustment signal to adjustclipping parameters, the clipper adjustment signal being generated inresponse to a combination of an environmental signal and an alteredversion of the gain control signal. In addition, the method may furthercomprise maintaining the variable power supply signal above a minimumvoltage level.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show more clearly howit may be carried into effect, reference will now be made, by way ofexample only, to the accompanying drawings which show exemplaryembodiments of the invention and in which:

FIG. 1 is a block diagram of an exemplary embodiment of a powermanagement system for a wireless communications device;

FIG. 2 is more detailed block diagram of the power management system ofFIG. 1;

FIG. 3 is a graph illustrating the relationship between theinstantaneous maximum power required by a power amplifier of a wirelesscommunication device and the power supply provided to the poweramplifier;

FIG. 4 is a block diagram of another embodiment of a power managementsystem for a wireless communications device;

FIG. 5 is a block diagram of another embodiment of a power managementsystem for a wireless communications device;

FIG. 6 is a graph illustrating the relationship between a desired powerlevel and a power control signal according to the embodiment of FIG. 5;

FIG. 7 a is flow chart showing the steps of a first calibration methodused to calibrate the power management system; and,

FIG. 7 b is a flow chart showing the steps of a second calibrationmethod used to calibrate the power management system.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those of ordinary skill in the artthat the invention may be practiced without these specific details. Inother instances, well-known methods, procedures and components have notbeen described in detail so as not to obscure the invention.

As is well understood, a wireless communications device generates aninternal data signal that is transmitted using a radio transmitter. Thedata signal is typically a comparatively low frequency signal that isgenerally referred to as a baseband signal. The baseband signal is mixedwith a carrier signal having a substantially higher frequency to producea transmission signal. The transmission signal is amplified in one ormore amplification stages of an output power amplification block toproduce an amplified transmission signal that is sufficiently powered sothat it is received with little or no data loss at a remote base stationor another communication device.

Typically, the amplification stages of the output power amplificationblock include a pre-amplification stage for producing a pre-amplifiedtransmission signal and a power amplification stage for producing theamplified transmission signal. The amplification level of thepre-amplification stage is controlled using a gain control block whichis typically implemented via a gain controller. The amplification levelis generally set using various open and/or closed loop methods fordetermining the desired power level of the amplified transmissionsignal. The pre-amplified transmission signal is then amplified again inthe power amplification stage to generate the amplified transmissionsignal. The gain of the power amplification stage is typically fixed butmay vary with the power supply level. The power amplification stage ispowered so that it can produce an amplified transmission signal that hasthe instantaneous maximum power that may be required for transmission.

The above power supply scheme for the power amplification stage may beacceptable in a wireless device in which the amplified transmissionsignal does not have a large dynamic range of power levels, or in whichthe amplified transmission signal has a very low peak-to-average powerratio (PAPR). However, in many cases, the amplified transmission signalhas a large dynamic range of power levels, in order to accommodate asignal that has a high PAPR, or to accommodate different types ofsignals that may have different desired power levels and differentPAPRs. The power amplification stage must be capable of generating anamplified transmission signal such that the highest instantaneous powerlevel desired for any data type or data rate of the baseband data thatis present in the amplified transmission signal is always accommodated.Accordingly, in conventional power management schemes, the poweramplification stage is always provided with a maximum amount of powersupply voltage that is sufficient for accommodating a specified maximuminstantaneous power level. However, much of the time, the actualinstantaneous power level of the amplified transmission signal may bewell below the specified maximum instantaneous power level therebyleading to inefficient operation of the power amplification stage duringsignal transmission. The excess power supplied to the power amplifier isdissipated as heat or otherwise lost.

The invention provides a power management system that supplies avariable power supply signal to a power amplification stage of an outputpower amplification block of a wireless communications device. Thedesired power of an amplified transmission signal, that is produced bythe power amplification stage, is estimated and used to vary the powersupply level to the power amplifier to reduce power loss in the poweramplification stage. Advantageously, to increase accuracy, the estimateddesired power is also based on at least one environmental informationsignal as is further discussed below.

Reference is first made to FIG. 1, which shows a block diagram of awireless communications device 10 having a data transmission block 12,an antenna 14, a receiver 16 and a power management system 18. Thewireless communications device 10 may be any type of wirelesscommunications device, such as an e-mail enabled personal dataassistant, a cellular phone, a portable computer, etc. FIG. 1 shows afirst exemplary embodiment of the power management system 18 accordingto the invention; other embodiments are shown in later Figures.

The data transmission block 12 includes a baseband device 20, anup-conversion block 22, and an output power amplification block 24. Theup-conversion block 22 includes a digital-to-analog converter (DAC) 26and a mixer 28. The output power amplification block 24 includes apre-amplifier 30, a filter 32 (which is optional), and a power amplifier34. The pre-amplifier 30 and the filter 32 implement thepre-amplification stage and the power amplifier 34 implements the poweramplification stage. The receiver 16 includes a power control datadetector, as is commonly known to those skilled in the art, forproviding power control information for the output power amplificationblock 24.

The power management system 18 includes an average power and gaincontrol block 36, a power supply level adjustment generator 38, a dataparameter detector 40 (which is optional), and a power supply means 42.The average power and gain control block 36 provides a gain controlsignal 44 to the pre-amplifier 30 and an average desired transmit powersignal 46 to the power supply means 42. The gain control signal 44 isprovided to the pre-amplifier 30 to control the gain of thepre-amplifier 30. The average desired transmit power signal 46 isgenerated based on at least one of a power control instruction signal 48and a received signal strength indicator signal 50 that is provided bythe receiver 16 based on signals received by the wireless communicationsdevice 10. The power supply means 42 also receives a power supply leveladjustment signal 52 from the power supply level adjustment generator 38and combines the average desired transmit power signal 46 and the powersupply level adjustment signal 52 to provide a variable power supplysignal 54 to the power amplifier 34. Preferably, this operation is inresponse to input changes including the power control instruction signal48 which is updated every 1.25 ms. The power supply level adjustmentgenerator 38 determines the additional adjustment provided by the powersupply level adjustment signal 52 based on the data type and data rateof the data that is to be transmitted by the communications device 10.The power supply level adjustment signal 52 can also preferably bevaried according to other parameters such as environmental parametersand the like that are described in further detail below.

The wireless communication device 10 communicates with remote basestations 58 and other devices through radio signals transmitted andreceived by the antenna 14. The base stations 58 transmit base stationradio signals 60 that are received by the antenna 14 and processed bythe receiver 16 to extract data from them, as is further describedbelow. This data path may be referred to as the forward link. Thewireless communications device 10 also transmits wireless device radiosignals 62 to the base stations 58 from the antenna 14. The data paththat begins at the wireless communications device 10 and ends at thebase stations 58 may be referred to as the reverse link.

In the forward link, the antenna 14 detects and receives one of the basestation radio signals 60 and provides a received signal 64 to thereceiver 16. The receiver 16 will typically include several functionalblocks, as is commonly known to those skilled in the art, to convert thereceived signal 64 into a digital signal and to process the receivedsignal 64 to remove noise, to perform down-conversion or demodulation,and the like. In many communications systems, including the IS-95 CodeDomain Multiple Access (CDMA) standard and subsequent communicationsstandards, the base stations 58 may transmit a series of power controlinstructions in the power control instruction signal 48 as part of thereceived signal 64. The power control instruction signal 48 instructsthe power management system 18 to increase or decrease the power of thetransmitted wireless device radio signals 62. In one standard, the powercontrol instruction signals 48 are sent in the form of data bits and maybe received at a rate of 800 power control bits per second. One of thebase stations 58 will send the power control instruction signal 48 basedon the quality of the wireless device radio signals 62 received by thebase station 58 from the wireless communications device 10. If thewireless device radio signal 62 is received with sufficient power toallow it to be decoded and used, then the base station 58 may instructthe wireless communications device 10 to maintain or reduce the power ofthe wireless device radio signal 62. If the wireless device radio signal62 is marginal or is too weak to be used, the base station 58 mayinstruct the wireless communications device 10 to increase the power ofthe wireless device radio signal 62. This type of power control istypically referred to as reverse link closed loop power control.

Some wireless communication systems, including systems which operateunder the IS-95 CDMA standard and subsequent standards, may also usereverse link open loop power control. Open loop power control isperformed by measuring the signal strength of the base station radiosignal 60 received by the wireless communications device 10. If thesignal strength of the base station radio signal 60 is high, then it isassumed that the wireless communications device 10 may transmit thewireless device radio signal 62 with lower strength and conversely, ifthe signal strength of the base station radio signal 62 is low, then itis assumed that the wireless device radio signal 62 must be stronger toreach the base radio station 58 in a usable form. This open loop powercontrol is based on the assumptions that: (i) the base radio station 58is transmitting the base station radio signal 60 with approximatelyconstant signal strength; and, (ii) the attenuation of the base stationradio signal 58 in the forward link will be about the same as theattenuation of the wireless device radio signal 62 in the reverse link.

The embodiments of the invention described herein are configured tooperate according to an open and closed loop power control scheme. Theembodiments of the invention can be configured to operate according toan open loop power control scheme by having the receiver 16 measure thesignal strength of the received signal 64 to provide the received signalstrength indicator signal 50. Accordingly, the received signal strengthindicator signal 50 corresponds to the signal strength of the basestation radio signal 60. In this case, the power control instructionscan be a combination of the open loop power instructions (derived fromthe received signal strength indicator signal 50) and closed loop powercontrol bits that are encoded in the control channel in the receivedbase station radio signals 60. In the absence of closed loop correctionsthe power control is based solely on the received signal strengthindicator signal 50.

Various detailed embodiments of the power management system 18 thatoperate according to an open and closed loop power control scheme willnow be discussed. Components that are identified with similar numbers ineach of the embodiments work in a similar fashion unless otherwisespecified. Referring now to FIG. 2, the average power and gain controlblock 36 includes an average power level block 66 and a gain controlblock 68. Further, the power supply means 42 includes a power supplycontrol block 70 and a switch converter 72.

The receiver 16 extracts the power control instruction signal 48 andpasses the signal 48 to the average power level block 66. The receiver16 also generates the received signal strength indicator signal 50 andpasses the signal 50 to the average power level block 66. The averagepower level block 66 combines the power control instruction signal 48and the received signal strength indicator signal 50 to calculate anaverage desired transmit power signal 46 for the wireless device radiosignal 62. Typically, the received signal strength indicator signal 50is used to set an initial power level when radio communication isestablished between the wireless communications device 10 and one of thebase stations 58. As the wireless communications device 10 is moved fromplace to place, it may communicate with different base stations 58 and aseamless “hand-off” between the base stations 58 is desirable. Tofacilitate this “hand-off”, when the wireless communications device 10initially begins communicating with a new base station 58, the averagepower level block 66 relies on the received signal strength indicatorsignal 50 to approximate the average desired transmit power signal 46.During ongoing communication between the wireless communications device10 and the base stations 58, the average desired transmit power signal46 is refined as instructions in the power control instruction signal 48are received from the base stations 58. The power control bits are “up”and “down” instructions which are time integrated and added to the openloop power. Over time, the average desired transmit power signal 46 maybe refined quite precisely to provide a balance between sufficient powerso that the wireless device radio signal 62 may be received by one ofthe base stations 58 in a usable form (i.e. it is not corrupted orundecodable due to interference from other signals or due to having alow signal strength) and so that the wireless device radio signal 62does not interfere with other devices communicating with the basestation 58 or other communication devices.

The baseband device 20 generates a baseband outgoing data stream 76 tobe transmitted to one of the base stations 58. Depending on the type ofservice that the baseband device 20 supports, the outgoing data stream76 may include only one type of data or may have different types of dataat different times. For example, some wireless communication devicesprovide multiple functions including e-mail communication, textmessaging, voice communication and other extended services. Differentservices may use different encoding and modulation methods that havedifferent PAPR characteristics. For example, in CDMA, even low data ratetraffic has a high PAPR after data modulation. As the data rateincreases, the PAPR increases further. The data parameter detector 40detects the type of data in the baseband outgoing data stream 76 inreal-time and provides the data parameter indication to the power supplylevel adjustment generator 38. Alternatively, and more preferably, thedata parameter indication can be provided directly to the power supplylevel adjustment generator 38 by the baseband device 20 in real-time.Hence, the solid arrow connecting the baseband device 20 to the powersupply level adjustment generator 38 and the use of dotted lines for thedata parameter detector 40 and the corresponding connections. The dataparameter indication includes information on the type of data, the datamodulation and the data rate in the baseband outgoing data stream 76.

The baseband outgoing data stream 76 is processed by the up-conversionblock 22 to convert it into a corresponding analog output signal 78. TheDAC 26 first converts the baseband outgoing data stream 76 into ananalog signal. The analog signal is then mixed with a carrier frequencyby the mixer 28 to produce the analog output signal 78 which is now inthe radio frequency range rather than the baseband. The mixing may beaccomplished in a single step or in multiple steps, depending on theimplementation, as is commonly known by those skilled in the art.Filtering may also be used. The carrier frequency is determined by thecommunications standard under which the wireless communications device10 operates, which is well understood by those skilled in the art. Inaddition, it should be noted that many wireless devices, including theexemplary wireless communications device 10, are capable of transmittinga wireless device radio signal 62 in more than one frequency band, andwithin more than one channel within each frequency band.

The power supply level adjustment generator 38 uses the data parameterindication of the baseband outgoing data stream 76 to determine thepower supply level adjustment signal 52. In the present embodiment, thepower supply level adjustment generator includes a PAPR mapper which maybe implemented by a look-up table. The look-up table is a discretelook-up table that is pre-computed by conducting tests on a prototypewireless communication device. Specifically, a value for a dataparameter is selected, such as a particular data rate test value, andgiven a fixed power supply level for the power amplifier 34, theheadroom is observed. A power supply level adjustment value is thenselected to reduce the headroom to a minimal level. The adjustment valueis then entered into the look-up table and associated with theparticular data rate test value. During operation, the data parameterindication (i.e. data type, data rate and data modulation) are then usedas indices into the look-up table to look up a value for the powersupply level adjustment signal 52. The power supply level adjustmentsignal 52 typically has a higher than nominal value if the data typerequires a high data bandwidth for transmission. The power leveladjustment signal 52 can also be varied based on environmental factorswhich are described in further detail below. The power level adjustmentsignal 52 is also adjusted at the upper and lower edges of the frequencyband in which the wireless device radio signals 62 are transmitted dueto the characteristics of the transmit chain. For exemplary purposes,the power level adjustment signal 52 may range from 0 to 9 dB dependingon the data type at a slew rate of 800 dB/second.

Typically, the manufacturer or vendor of the wireless communicationsdevice 10 will configure a PAPR mapper in the power supply leveladjustment generator 38 to provide suitable values for the power leveladjustment signal 52 for different data types, data modulation and datarate as well as other parameters that are further described below. ThePAPR mapper is discussed in further detail below. This is accomplishedby following a calibration method that is described in further detailbelow.

In an alternative embodiment of the invention, the PAPR mapper may beimplemented using a formula based on the relationship between thevarious inputs to the power supply level adjustment generator 38 and thecorresponding value of the power level adjustment signal 52 rather thanusing a look-up table.

The average desired transmit power signal 46 is supplied to the gaincontrol block 68, which converts the average desired transmit powersignal 46 into a gain control signal 44. The gain control block 68 maybe implemented as a look-up table that has been calibrated to achieve adesired average transmitted power level at the antenna 14 that is inaccordance with the average desired transmit power signal 46. Thelook-up table in the gain control block 68 compensates for bothnon-linearities in the control characteristic of the pre-amplifier 30and the gain variation of the power amplifier 34 that is caused by thechange in the power supply voltage level that is provided to the poweramplifier 34. The content of the look-up table is written during factorycalibration of the wireless communications device 10 based on thereceived signal strength indicator signal 50 and the observedtransmitter power at the device's antenna port. Gain values in thelook-up table are calculated based on the received signal strengthindicator signal 50 which are then offset by the control bits in thepower control instruction signal 48. During operation, linearinterpolation can be performed for values within the table.

The pre-amplifier 30 receives the analog output signal 78 and amplifiesunder the control of the gain control signal 44 to produce apre-amplified transmission signal 82. The gain control signal 44 isgenerated so that an increase or decrease in the average desiredtransmit power signal 46 produces a log-linear increase or decrease inthe amplification of the output power amplifier block 24, throughadjusting the gain of the pre-amplifier 30.

The pre-amplified transmission signal 82 is filtered by the filter 32 toproduce a filtered transmission signal 84. The filter 32 removes noisethat is introduced into the pre-amplified transmission signal 82 by thepre-amplifier 30 and prior stages of the wireless communications device10. The specific characteristics of the filter 32 such as the passbandfrequency range, the filter order and the like, will depend on thespecific pre-amplifier 30 and the prior stages that are used in thewireless communications device 10. A skilled person in the art will becapable of selecting appropriate parameters for the filter 32. It shouldbe noted that the filter 32 is optional and may be omitted in caseswhere the pre-amplified transmission signal 82 is sufficiently free ofnoise.

The filtered transmission signal 84 is amplified by the power amplifier34 to provide an amplified transmission signal 86. The amplifiedtransmission signal 86 is transmitted by the antenna 14 as the wirelessdevice radio signal 62. The amplified transmission signal 86 hassufficient power so that it may be received by any one of the basestations 58 in a form that is receivable and decodable to re-create thebaseband outgoing data stream 76.

The average and peak power levels of the amplified transmission signal86 vary over time. As the average desired transmit power signal 46varies, the amplitude of the pre-amplified transmission signal 82 willvary. The power amplifier 34 will typically have a constant gain factorand accordingly, the amplified transmission signal 86 will also have atime-varying average power level. The power amplifier 34 may also have again factor that varies with the power supply voltage level, but thisvariation may be compensated using calibration tables as is well knownin the art. When the analog output signal 78 has a high PAPR, theinstantaneous power level of the amplified transmission signal 86 willalso vary. At any point in time, the power amplifier 34 requiressufficient power to operate its internal electronics and to produce theamplified transmission signal 86. When the amplified transmission signal86 has its maximum instantaneous power level (i.e. during a maximum peakof the amplified transmission signal 86 which corresponds with thehighest possible value for the average desired transmit power signal46), the power amplifier 34 must still have at least some headroom toensure that the amplified transmission signal 86 is not clipped at itspeaks. One reason for the significant power loss that occurs in theoutput power amplifier block 24 of the wireless communication device 10is that the amplified transmission signal 86 is rarely at this maximumlevel and is usually at a much lower power level. The excess headroombetween the power supply level provided to the power amplifier 34 andthe magnitude of the amplified transmission signal 86 is dissipated asheat.

To avoid this power loss, the power supply level adjustment signal 52and the average desired transmit power signal 46 are combined by thepower supply control block 70 to generate a power control signal 90,which may be a pulse width modulated or pulse density modulated signal.The power control signal 90 is converted into the variable power supplysignal 54, which is an analog signal, by the switch converter 72. Thevariable power supply signal 54 is the source of power supply for thepower amplifier 34. The variable power supply signal 54 has a magnitudesuch that there is a small, yet sufficient, amount of headroom above themaximum instantaneous power required to produce the amplifiedtransmission signal 86 with a desired quality and for the poweramplifier 34 to sufficiently operate its internal electronics. Anexemplary value for the required headroom is on the order of 1 to 3 dB.As manufacturing consistency increases for manufacturing the variouscomponents of the wireless communications device 10 and the powermanagement system 18, the headroom can be reduced.

Referring now to FIG. 3, shown therein is a graph of an exemplaryrelationship between the instantaneous maximum power required by thepower amplifier 34 to produce the amplified transmission signal 86 andthe variable power supply signal 54. This relationship may varydepending on the implementation of the power management system 18 andthe components used in the wireless communications device 10. Thevariable power supply signal 54 is generally slightly greater than aminimum voltage level 92 required by the power amplifier 34 at any pointin time to produce the amplified transmission signal 86 with apredefined required quality. The variable power supply signal 54 willvary in time, corresponding to changes in the average desired transmitpower signal 46 and changes in the data parameter indication of thebaseband outgoing data stream 76 being transmitted by the wirelesscommunications device 10. In another embodiment of the power managementsystem 18, the variable power supply signal 54 will also preferably varydue to changes in the environment of the wireless communications device10 (such as temperature), changes in condition of the battery thatpowers the wireless communications device and changes in the frequencyrange in which the wireless device radio signal 62 is being transmitted.

As previously mentioned, the variable power supply signal 54 has aminimum voltage level 92, which is selected to ensure that even when theinstantaneous maximum power required by the power amplifier 34 togenerate the amplified transmission signal 86 is low, sufficient poweris supplied to the power amplifier 34 to keep it stable and to keep itsinternal electronics functioning. The minimum voltage level 92 may bemaintained by the power supply control block 70(which can maintain thepower control signal 90 above the minimum voltage level 92) or theswitch converter 72 which can directly maintain the variable powersupply signal 54 above the minimum voltage level 92. An exemplary rangeof values for the minimum voltage level is 0.9 to 1.4 Volts depending onthe design of the power amplifier 34.

The power management system 18 reduces the headroom between the level ofthe variable power supply signal 54 that is supplied to the poweramplifier 34 and the supply power required for the power amplifier 34 togenerate the amplified transmission signal 86 without clipping. Thisreduction in headroom reduces the amount of power dissipated in thepower amplifier as heat. Overall, the reduced power loss cansubstantially improve the power efficiency and battery life for thewireless communications device 10, since one of the largest areas ofpower loss in many wireless devices is excess power headroom in thepower amplifier.

The power management system 18 may be modified in various ways withinthe scope of the invention. For instance, in some cases, it may bedesirable to apply an analog power supply signal to the switch converter72. To do so, a DAC may be coupled between the power supply controlblock 70 and the switch converter 72. This is done when the switchconverter control 72 is analog. In addition, it may be desirable tofilter high frequency noise from the variable power supply signal 54,particularly if a DAC is used to produce an analog power supply signal.This may particularly be required if a delta-sigma converter is used tomake the D/A conversion, rather than a linear DAC. The filter in thiscase may be inserted at the input of the switch converter 72.

In another alternative embodiment of the invention, it may be desirableto insert a buffer (not shown) to temporally align the variable powersupply signal 54 and the filtered transmission signal 84 at the poweramplifier 34 (i.e. the supply voltage to the power amplifier 34 ispreferably updated at the same rate as the updating of the gain controlsignal 44). If the data path between the output of the baseband device20 and the input of the power supply control block 70 delays thevariable power supply signal 54 in comparison to the arrival of the dataat the input of the power amplifier 34, it is possible that at times,the power amplifier 34 may not have sufficient headroom to produce theamplified transmission signal 86. To synchronize the variable powersupply signal 54 and the filtered transmission signal 84, a data buffer(not shown) may be inserted between the baseband device 20 and the DAC26, after the point at which the baseband device 20 is connected to thepower management system 18. The buffer may be configured to introduce anappropriate delay, based on the delay introduced by the various elementsof the power management system 18.

Referring now to FIG. 4, shown therein is an alternative embodiment of apower management system 18′ which includes an environmental sensor unit93 that is connected to the power supply level adjustment generator 38for providing at least one environmental information signal. Theenvironmental sensor unit 93 includes one or more environmental sensorsfor sensing variations in parameters that can affect the characteristicsof the power amplifier 34 and hence the level of the variable powersupply signal 54. For instance, the level of the variable power supplysignal 54 in response to the ambient temperature of the wirelesscommunications device 10, the condition of the battery that powers thewireless communications device 10 and/or the frequency at which thewireless device radio signal 62 is transmitted.

The environmental sensor unit 93 can include a temperature sensor 94 forsensing the ambient temperate of the hardware of the wirelesscommunications device 10 and provide a temperature information signal 96to the power supply level adjustment generator 38. The temperatureinformation signal 96 will preferably be in a digital form. If thetemperature sensor 94 provides analog temperature information, ananalog-to-digital converter (ADC) may be coupled between the temperaturesensor 94 and the power supply level adjustment generator 38 to convertthe analog temperature information signal 96 into a digital temperatureinformation signal. The temperature information signal 96 may be passedto the power supply level adjustment generator 38 using shared memory orany other data transfer mechanism commonly known to those skilled in theart.

The environmental sensor unit 93 can include a battery condition sensor98 for sensing the charge level of the battery that is used to power thewireless communications device 10 to provide a battery conditioninformation signal 100 to the power supply level adjustment generator38. As in the case of the temperature sensor 94, an ADC may be used toconvert an analog battery condition information signal into acorresponding digital battery condition information signal. Further, thedigital battery condition information signal 100 may be passed to thepower supply level adjustment generator 38 using techniques known tothose skilled in the art. The battery condition is sensed so that thepower supply level of the power amplifier 34 can be increased in theevent that the analog output signal 78 that is passing through theoutput power amplifier block 24 has a high PAPR. In this case,adjustments are made to the power supply level adjustment signal 52 tocompensate for the anticipated compression due to the lower charge ofthe battery.

The environmental sensor unit 93 can also provide a frequencyinformation signal 104 to provide information on the operating (i.e.transmission) frequency of the wireless device radio signals 62 to thepower supply level adjustment generator 38. The operating frequency canbe obtained from the baseband device 20 or the up-conversion block 22.As in the case of the temperature sensor 94 and the battery conditionsensor 98, an ADC may be used to provide the frequency informationsignal 104 as a corresponding digital frequency information signal.

The power supply level adjustment generator 38 combines the dataparameter indication of the baseband outgoing data stream 76 with atleast one of the temperature information signal 96, the batterycondition information signal 100 and the frequency information signal104 to determine the power supply level adjustment signal 52. In thiscase, the power supply level adjustment generator 38 can utilize amulti-dimensional look-up table. To reduce, complexity a two-dimensionallook-up table may be used. The data parameter indication, temperatureinformation signal 96, battery condition information signal 100 and thefrequency information signal 104 are used as indices into the look-uptable to look up a value for the power supply level adjustment signal52. Alternatively, the content of the look-up table can be updated whenthere are changes in the operating frequency channel or temperature. Theeffects of frequency and temperature are used to scale the contents ofthe two-dimensional look-up table by +/− a few dB. In anotheralternative, there can be a plurality of PAPR mappers, with one PAPRmapper being provided for the temperature information signal, one PAPRmapper being provided for the battery condition information signal andone PAPR mapper being provided for the operating frequency. In thiscase, the outputs of the PAPR mappers, which are in units of dB, can beadded together to obtain the power supply level adjustment signal 52.Logarithmic combination may be used if the amplitude of the outputs ofthe PAPR mapper are not in dB. In either case, factory calibration isdone to determine the effect of the environmental parameters on thepower supply level adjustment value. For instance, the device 10 can beput into an environmental chamber and the temperature adjusted to acertain value to determine the effect on the power supplylevel-adjustment value for a certain data parameter value. With regardsto battery condition, the level of the battery of the device 10 can beadjusted to different values to determine the effect on the power supplylevel adjustment value for a certain data parameter value. With regardsto operating frequency, the transmission frequency can be varied todetermine the effect on the power supply level adjustment value for acertain data parameter value.

The power supply level adjustment signal 52 is typically larger than anominal value if (a) the data parameter indicates a high data bandwidthfor transmission; (b) the temperature increases; or (c) the charge levelof the battery decreases. Collectively, the adjustment due totemperature, battery condition and operating frequency can have asubstantial effect on the value of the power supply level adjustmentsignal 52.

The power supply level adjustment generator 38 is configured to providesuitable values for the power supply level adjustment signal 52 fordifferent data types, data modulation and data rate as well asenvironmental information (i.e. temperature and battery), frequencyinformation. The power supply level adjustment signal 52 is typically onthe order of +/−1-3 dB for a temperature variation, +/−1 dB for batterylevel variation and +/−1-3 dB for a transmission frequency variation.

Some embodiments of the invention may be implemented in a powermanagement system 18″ that does not allow access to the average desiredtransmit power signal 46. FIG. 5 illustrates an alternative embodimentfor the power management system 18″ in which the average power and gaincontrol block 36 is implemented as a single block. As a result, theaverage desired transmit power signal 46 is not available as an inputfor the power supply means 42. In addition, the average power and gaincontrol block 36 operates as a hybrid of a lookup table and aninterpolator. The power control instruction signal 48 and the receivedsignal strength indicator signal 50 indicate a desired average supplypower level as described previously. The average power and gain controlblock 36 provides the gain control signal 44 in response to the desiredaverage supply power level.

In this case, the power supply means 42 comprises a summer 110, areverse mapper 112, a clipper 114 and the switch converter 72. Thesummer 110 receives the gain control signal 44 and an altered version ofthe power supply level adjustment signal 52′ to provide a first powercontrol signal 90′. The altered version of the power supply leveladjustment signal 52′ is provided by the power supply level adjustmentgenerator 38′ so that the power supply level adjustment signal 52′ canbe directly summed with the gain control signal 44. Typically, the gaincontrol signal 44 has units of Volts and the power supply leveladjustment signal 52 has units of dB so that these two signals cannot bedirectly summed together. Accordingly, the power supply level adjustmentgenerator 38′ scales the power supply level adjustment signal 52 toprovide the altered signal 52′. In particular, the scaling is done basedon the generation of the gain control signal 44 in the average power andgain control block 36 which depends on parameters that define thelook-up table in the average power and gain control block 36. Theseparameters are known prior to the commercial use of the wirelesscommunications device 10 and hence are available for use in the powersupply level adjustment generator 38′.

The first power control signal 90′ is then provided to the clipper 114which has a positive and negative saturation value and a slope thatconnects these two values. The clipper 114 operates on the first powercontrol signal 90′ to provide a second power control signal 90″ to theswitch converter 72. The switch converter 72 then generates the variablepower supply signal 54 as previously described. A DAC may also be usedas described previously.

The clipper 112 may clip the first power control signal 90′ orattenuate/compress the first power control signal 90′ according to theslope, based on the magnitude of the first power control signal 90′. Thepositive and negative saturation values and the slope of the clipper 112can be varied in response to the operation of the power managementsystem 118″. In particular, the look-up table that is used in theaverage power and gain control block 36 and the environmentalinformation 116 that is provided by the environmental sensor unit 93 viathe power supply level adjustment generator 38′ can be used to vary thepositive and negative saturation values and the slope of the clipper112. In particular, the environmental information 116 and an alteredversion of the gain control signal 44′ are provided to the reversemapper 112 which then provides a clipper adjustment signal 118 to theclipper 114. The contents of the signal 44′ are derived from the data inthe look-up table of block 36. The connection lines are shown asdash-dotted lines since the adjustment of the clipper due to the signals44 and 116 occurs at a slower rate compared to the rate of change of thepower supply level adjustment signal 52′. In particular, themodification occurs when there is a change in the look-up table used inblock 36 or when there is a substantial change in the environmentalinformation 116 (i.e. there is a drastic change in temperature or ahand-off in transmission frequency). For instance, the maximumsaturation value is related to operating frequency. The clipper 114 ismodified in this fashion to optimize the variable power supply signal 54and hence the power savings in the power amplifier 34. The summer 110,clipper 114 and the switch converter 72 are preferably implemented viahardware and the reverse mapper 112 is preferably implemented viasoftware, although other implementations for these blocks is possible.

FIG. 6 illustrates the operation of the average power and gain block 36.As the average desired power supply level rises and falls, the averagepower and gain control block 36 either selects a pre-determined value(identified by solid dots) or interpolates between pre-determined valuesto calculate a value for gain control signal 44. Preferably, the averagepower and gain control block selects the closest pre-determined valuewhen generating the gain control value 44 to avoid interpolation errors.In practice, the range associated with FIG. 6 is about −52 to 26 dBm.The pre-determined values are programmed into the average power and gainblock 36 by a manufacturer, vendor or operator of the wirelesscommunications device 10.

The power management system 18″ provides a practical implementation ofthe invention that may be used with commercially available basebandchipsets in a device in which the average desired transmit power signal46 is not available as an input to the power supply means 42.

In each of the embodiments of the invention shown herein, the PAPRmapper may provide a value for the power supply level adjustment signalevery 20 ms. In some cases, a value for the power supply leveladjustment signal may be provided every 5 ms. Further, in some cases, itis preferable to update the supply voltage of the power amplifier 34every 1.25 ms to guarantee that the ACPR (adjacent channel power ratio)limits are never violated. In addition, the mapping that is performed bythe power supply level adjustment generator 38 is such that thetransition from a low power supply voltage to a high power supplyvoltage for the power amplifier 34 is a consistent and smooth functionof the desired average power level to reduce non-linearities that areintroduced by the various embodiments of the power management system 18.

As shown in FIG. 3, the power supply control block 70 applies a lineartransformation to a combination of the average desired transmit powersignal 46 and the power supply level adjustment signal 52. Thetransformation is applied via a look-up table or via an equation. Theequation can be implemented in software or hardware. The exact shape ofthe transformation is adjusted to tune performance and production yield.Accordingly, the power supply control block 70 is preferably calibratedbefore use.

Referring now to FIG. 7 a, shown therein is a flowchart showing thesteps of a power supply block calibration method 120. The calibration isdone at a given reference temperature, and a given reference batterycondition that are arbitrarily chosen. The baseband device 20 isconfigured to transmit at an arbitrarily chosen reference transmissionfrequency. The power supply level adjustment value generator 38 is thenconfigured such that the contributions from the reference temperature,reference battery condition and reference frequency is set to zero. Thefirst step 122 of the calibration method is to transmit the wirelessdevice radio signals 62 at a constant power level while the ACPR ismonitored. The next step 124 is to reduce the magnitude of the variablepower supply signal 54 to the power amplifier 34 while maintainingconstant output power in the wireless device radio signals 62. This isdone by increasing the input drive to the power amplifier 34 as thesupply voltage to the power amplifier 34 is decreased to maintainconstant output power. The next step 126 is to note the magnitude of thevariable power supply level signal 54 when the ACPR has increased to apre-specified design target. The ACPR is defined as the ratio of thepower at 1.25 MHz offset within a 30 kHz bandwidth to the power in thecarrier. As the linearity of the -power amplifier 34 is reduced bystarving its power supply the compression artifacts increase. The nextstep 128 in the calibration method 120 is to increase the output powerof the wireless device radio signals 62 and to repeat steps 122,124 and126. The step size that is used to determine the next power leveldepends on the implementation of the power amplifier 34 and thoseskilled in the art will understand how to select the step size. Step 128is repeated for several output power levels. The number of output powerlevels that are used for calibration depends on the implementation ofthe power amplifier. Typically, three, well-spaced output power levelscan be used for calibration.

The next step 130 is to use the control curves of the switchingconverter 72 and the minimum voltage level 92 to compute an idealtransfer function that is required to derive the digital power signal 90for controlling the switch converter 72. The ideal transfer function isrelated to the look-up table used in the average power and gain controlblock 36 or the gain control block 68. The construction of the look-uptable was previously described. The next step 132 is to repeat steps 122to 130 for several different wireless communication devices to obtain anaverage transfer function.

The next step 134 is to perform curve fitting on the average transferfunction. One way to accomplish this is by fitting a linear line to theaverage transfer function by adjusting the slope and the intercept ofthe straight line to fit the average transfer function with minimalerror. The slope that is determined is used by the power supply controlblock 70 as one of the parameters for varying the power supply biasvoltage, the ramp slope or the idle bias current. The intercept is setby the breakeven power of the output amplifier block 24 which is thepoint at which further reduction in the variable power supply signal 54to the power amplifier 34 (and consequently gain) causes the earlierstages in the output amplifier block 24 to use so much additional powerthat the total power consumption of the wireless communications device10 is increased. The intercept coincides with the minimum voltage level92. The parameters determined by curve fitting is then used to create alook-up table for the power supply block 70.

Referring now to FIG. 7 b, shown therein is a flowchart showing thesteps of a power supply level adjustment generator calibration method140. The calibration method 140 is preferably performed on a per devicebasis during factory calibration to account for variations in productiontolerance and deviations from the average transfer function model thatwas obtained for the power supply control block 70. The first step 142of the calibration method 140 is to load the power supply adjustmentlevel generator 38 with a value that causes the switching converter 72to operate at its minimum output voltage. This allows the calibrationmethod 140 to start at the lowest transmission power point of thewireless communications device 10.

The next step 144 is to calibrate the transmission power using the usualprocedure according to the transmission power point defined in step 142.The usual procedure involves increasing the automatic gain control ofthe device 10 over a predefined “safe” range and recording thetransmitter output power. Preferably, half of the range is calibratedfirst. This is done until the output power of the wirelesscommunications device slightly exceeds a target power as determined forthe set supply voltage. The target power is obtained duringcharacterization of the wireless communication device 10 as is commonlyknown to those skilled in the art. The characterization will depend onthe manufacturer of the components of the output power amplifier block24. The target power is the breakeven point that is determined byreducing the power supply level to the power amplifier 34 anddetermining the point at which the pre-drive circuitry consumes so muchpower that the savings in power amplifier power dissipation (by reducingheadroom) is mitigated.

The next step 146 is to interpolate the output value of the averagepower and gain control block 36 and load this interpolated output value,after appropriate adjustment by the reverse mapper 112, into the powersupply level adjustment generator 38. The next step 148 is to adjust thetransmission power level to a value that is slightly below the targetpower.

The next step 150 is to increase the value of the transmission powerlevel and repeat steps 142 to 148 of the calibration method 140. Thecalibration method 140 is continually repeated until a maximum specifiedtransmission power point is reached.

The invention has been described here by way of example only. Variousmodifications and variations may be made to these exemplary embodimentswithout departing from the spirit and scope of the invention, which islimited only by the appended claims.

1. A power management system for providing a variable power supplysignal to an output power amplifier block in a wireless communicationdevice, the power management system comprising: (a) an average power andgain control block for providing a gain control signal in response to atleast one of a power control instruction signal and a received signalstrength indicator signal and providing the gain control signal to theoutput power amplifier block; (b) an environmental sensor unit forproviding at least one environmental information signal; (c) a powersupply level adjustment generator connected to the environmental sensorunit for providing an altered version of a power supply level adjustmentsignal in response to a data parameter indication of a baseband outgoingdata stream to be transmitted by the wireless communication device andthe at least one environmental information signal; and, (d) a powersupply means connected to the average power and gain control block andthe power supply level adjustment generator, the power supply meansprovides the variable power supply signal to the output power amplifierblock by providing a first power control signal based on the gaincontrol signal and the altered version of the power supply leveladjustment signal, clipping the first power control signal to provide asecond power control signal and generating the variable power supplysignal based on the second power control signal, wherein, the gaincontrol signal is adapted for applying sufficient gain to a transmissionsignal version of the baseband outgoing data stream and the alteredversion of the power supply level adjustment signal is adapted forproviding a small sufficient amount of headroom to efficiently providepower to transmit the transmission signal.
 2. The power managementsystem of claim 1, wherein the environmental sensor unit comprises atleast one of: (e) a temperature sensor for providing a temperatureinformation signal as part of the at least one environmental informationsignal, the temperature information signal being related to thetemperature of the hardware of the wireless communications device; and,(f) a battery condition sensor for providing a battery conditioninformation signal as part of the at least one environmental informationsignal, the battery condition information signal being related to abattery used to power the wireless communication device.
 3. The powermanagement system of claim 1, wherein the at least one environmentalinformation signal comprises a frequency information signal related tothe frequency at which the baseband outgoing data stream will betransmitted.
 4. The power management system of claim 1, wherein theaverage power and gain control block provides an altered version of thegain control signal and the power supply means comprises: (g) a summerconnected to the average power and gain control block and the powersupply level adjustment generator for summing the gain control signaland the altered version of the power supply level adjustment signal togenerate the first power control signal; (h) a clipper connected to thesummer for receiving the first power control signal and generating thesecond power control signal; (i) a switch converter connected to theclipper for receiving the second power control signal and generating thevariable power supply signal; and, (j) a reverse mapper connected to thepower supply level adjustment generator and the average power and gaincontrol block for receiving an environmental signal and the alteredversion of the gain control signal respectively and generating a clipperadjustment signal, the reverse mapper also being connected to theclipper for providing the clipper adjustment signal to the clipper foradjusting the positive and negative saturation values and slope of theclipper.
 5. The power management system of claim 1, wherein the powersupply means is configured to maintain the variable power supply signalabove a minimum voltage level.
 6. The power management system of claim1, wherein the power supply level adjustment generator is implemented bya plurality of look-up tables, wherein one look-up table is provided foreach environmental information signal and the data parameter indication,and the outputs of each look-up table are combined to generate thealtered version of the power supply level adjustment signal.
 7. Thepower management system of claim 6, wherein at least one of the look-uptables is implemented by a formula based on a relationship between thevarious inputs to the power supply level adjustment generator and thealtered version of the power level adjustment signal.
 8. The powermanagement system of claim 1, wherein the system further comprises adata parameter detector connected to the power supply level adjustmentgenerator and a baseband device of the wireless communications device,wherein the data parameter detector provides the data parameterindication.
 9. The power management system of claim 1, wherein the powersupply means comprises a switch converter configured to generate thesecond power control signal based on the second power control signal,wherein the power supply means is calibrated by: (i) transmittingwireless device radio signals at a constant power level from thewireless communication device while monitoring an Adjacent Channel PowerRatio (ACPR); (ii) reducing the magnitude of the variable power supplysignal while maintaining constant output power in the wireless deviceradio signals; (iii) recording the magnitude of the variable powersupply signal when the ACPR has increased to a pre-specified designtarget; (iv) increasing the output power of the wireless device radiosignals and repeating steps (i) to (iii) for several output powerlevels; and, (v) computing an ideal transfer function for deriving thesecond power control signal for controlling the switch converter. 10.The power management system of claim 9, wherein the power supply meansis further calibrated by: (vi) repeating steps (i) to (v) for severaldifferent wireless communication devices to obtain an average transferfunction; and, (vii) performing curve fitting on the average transferfunction.
 11. The power management system of claim 9, wherein the powersupply level adjustment generator is calibrated by: (viii) loading thepower supply level adjustment generator with a value which causes theoutput power amplifier block to operate at a lowest transmission powerpoint; (ix) calibrating transmission power level until the output powerof the output power amplifier block slightly exceeds a target powerdetermined for a power supply voltage level; (x) interpolating theoutput value of the average power level and gain control block andloading this interpolated output value, after adjustment by a reversemapper, into the power supply level adjustment generator; (xi) adjustingthe transmission power level to a value slightly below the target power;and, (xii) increasing the value of the transmission power level andrepeating steps (viii) to (xi) until a maximum specified transmissionpower point is reached.
 12. The power management system of claim 1,wherein positive and negative saturation values and slope used inclipping are adjusted based on the at least one environment signal andthe altered version of the gain control signal.
 13. A wirelesscommunications device comprising the power management system of claim 1.14. A method of supplying a variable power supply signal to an outputpower amplifier block in a wireless communications device that receivesan incoming data stream from a base station radio signal and transmitsan outgoing data stream in a wireless device radio signal, the methodcomprising: (a) detecting at least one of a signal strength of the basestation radio signal to produce a received signal strength indicatorsignal, and a power control instruction signal in the base station radiosignal; (b) generating as an output a gain control signal in response toat least one of the received signal strength indicator signal and thepower control instruction signal; (c) generating at least oneenvironmental information signal for obtaining information about theenvironment of the wireless communications device (d) generating analtered version of a power supply level adjustment signal based on adata parameter indication of a baseband outgoing data stream and the atleast one environmental information signal; (e) providing a first powercontrol signal based on the gain control signal and the altered versionof the power supply level adjustment signal, clipping the first powercontrol signal to provide a second power control signal, and generatingthe variable power supply signal based on the second power controlsignal; and, (f) providing the variable power supply signal and the gaincontrol signal to the output power amplifier block, wherein, the gaincontrol signal is adapted for applying sufficient gain to a transmissionsignal version of the baseband outgoing data stream and the alteredversion of the power supply level adjustment signal is adapted forproviding a small sufficient amount of headroom to efficiently providepower to transmit the transmission signal.
 15. The method of claim 14,wherein step (c) comprises at least one of: (i) generating a temperatureinformation signal related to the temperature of the hardware of thewireless communications device and providing the temperature informationsignal as part of the at least one environmental information signal;(ii) generating a battery condition information signal related to abattery used to power the wireless communications device and providingthe battery condition information signal as part of the at least oneenvironmental information signal; and, (iii) generating a frequencyinformation signal related to the frequency at which the outgoing datastream is transmitted and providing the frequency information signal aspart of the at least one environmental information signal.
 16. Themethod of claim 14, wherein step (e) comprises: (iv) adding the alteredversion of the power supply level adjustment signal and the gain controlsignal to provide the first power control signal, the altered version ofthe power supply level adjustment signal being generated based on thederivation of the gain control signals.
 17. The method of claim 16,wherein step (v) comprises generating an altered version of the gaincontrol signal and providing a clipper adjustment signal to adjustpositive and negative saturation values and slope used in clipping, theclipper adjustment signal being generated in response to a combinationof the at least one environmental information signal and the alteredversion of the gain control signal.
 18. The method of claim 14, whereinthe method further comprises maintaining the variable power supplysignal above a minimum voltage level.
 19. A method of calibrating apower management system for a wireless communication device having anoutput power amplifier block, wherein the power management systemcomprises a power supply control block configured to provide a powercontrol signal and a switch converter configured to provide a variablepower supply signal to the output power amplifier block in response tothe power control signal, wherein the method comprises: (i) transmittingwireless device radio signals at a constant power level from thewireless communication device while monitoring an Adjacent Channel PowerRatio (ACPR); (ii) reducing the magnitude of a variable power supplysignal while maintaining constant output power in the wireless deviceradio signals; (iii) recording the magnitude of the variable powersupply signal when the ACPR has increased to a pre-specified designtarget; (iv) increasing the output power of the wireless device radiosignals and repeating steps (i) to (iii) for several output powerlevels; and (v) computing an ideal transfer function for deriving thepower control signal for controlling the switch converter.
 20. Themethod of claim 19, wherein the method further comprises calibrating thepower supply means by: (vi) repeating steps (i) to (v) for severaldifferent wireless communication devices to obtain an average transferfunction; and, (vii) performing curve fitting on the average transferfunction.
 21. The method of claim 19, wherein the power managementsystem further comprises an average power and gain control blockconfigured to provide a gain control signal to the output poweramplifier block and an average desired transmit power signal to thepower supply control block, and a power supply level adjustmentgenerator configured to provide a power supply level adjustment signalto the power supply control block and the method further comprises:(viii) loading the power supply level adjustment generator with a valuewhich causes the output power amplifier block to operate at a lowesttransmission power point; (ix) calibrating transmission power leveluntil the output power of the output power amplifier block slightlyexceeds a target power determined for a power supply voltage level; (x)interpolating the output value of the average power level and gaincontrol block and loading this interpolated output value, afteradjustment by a reverse mapper, into the power supply level adjustmentgenerator; (xi) adjusting the transmission power level to a valueslightly below the target power; and, (xii) increasing the value of thetransmission power level and repeating steps (viii) to (xi) until amaximum specified transmission power point is reached.